Fix caching bug in ROOTClassEnhancer::IsA
Fix caching bug in ROOTClassEnhancer::IsA

When looking up the value of a cache in the map, it was possible
to temporarily have fLastClass and fLastType out of synch and cause
the program to return the wrong TClass.

Dr15Jones/root,Dr15Jones/root,Dr15Jones/root,Dr15Jones/root,Dr15Jones/root,Dr15Jones/root,Dr15Jones/root